Dry pH probe

[Malum Argenteum]

I was shipped a dry pH probe by an online vendor. The vendor assured me that this is 'normal' and I shouldn't worry. I called Neptune (it is a Neptune probe) and they said the same. So I calibrated it, and it seemed to be acting normallly. This morning, the meter (Apex) was reading 0.7 units high. (This runs CO2 injection on a planted tank, so things are bad right now.)

Can I expect this probe to stabilize?

 

[epon]

I just had this happen on a pinpoint, called the vendor and got the same story but then wondered why we're told to always keep them wet. Tagging along here...

 

[Malum Argenteum]

epon, did you end up using the dry probe?

 

[125mph]

According to BRS, if the probe is dry, just soak it in PH 4.0 solution for a few hours and problem solves.. LOL... I would return the probe though. I like all the stuff I buy to be 100% without uncertainty.

 

[mcgyvr]

How do you know it was high this morning?
Did you calibrate again?
PH changes during the day,etc.....

 

[epon]

epon, did you end up using the dry probe?

I'm still a few days from adding that on a new system so I havn't. Was told by the vendor that if it wasn't working to send it back.

 

[Malum Argenteum]

I knew it was high because (1) all fish in the tank were struggling to breathe (excess CO2), and (2) I then checked pH of water from that tank using the probe on my reef (separate Apex unit).

I haven't recalibrated yet -- I used all my 7.0 solution yesterday, since I was nervous about using the dry probe and calibrated it twice and then calibrated the probe on my reef system, too, so I could trust it to check my results. And I used a couple packets checking to see that they calibrated right.

Yeah, I should've returned the probe unused. I trusted that Neptune knew best, though... I guess not.

 

[epon]

Out of curiosity how dry was the probe? Sat in the air of a bubble in the cap or 0 liquid in the cap?

 

[Malum Argenteum]

Out of curiosity how dry was the probe? Sat in the air of a bubble in the cap or 0 liquid in the cap?

Zero liquid in the cap. Bone dry. Salty crystals on the seam where the cap meets the probe.

 

[Malum Argenteum]

Here's what BRS says:
***
Jason (BulkReefSupply)
Jan 13, 11:41 CST

Hey There,
Great Question! This is certainly accurate, around the office we use probes that have been dry for quite some time with no issues at all. If you have any other questions, let us know!

Jason

John Zillmer
Jan 13, 10:59 CST

Hi,

I talked to a customer rep at Neptune recently, and was told that their pH probes will sometimes dry out before they are shipped to customers, and that this is normal and nothing to worry about. What is your opinion?

Thanks,
John
***
I guess I'll let it sit a few days and recalibrate and keep an eye on it. It sure is screwed up now, though.

 

[epon]

I wish you luck, mine was just bubbles that the tip sat in which is different that what Ive gotten in the past. Maybe mine will be ok.

 

[Malum Argenteum]

I have some more calibration solution on order, so I'll update this next week after it sits a while and I recalibrate.

 

[DDon]

Here is an article for restoring the hydration layer on a dry probe.
http://www.all-about-ph.com/ph-glass.html

For another reference from Hannah Instruments recommends soaking in storage solution for 3-4 hours to rehydrate. Storage solution is just a simple KCl solution you can either buy or make yourself.
http://hannainst.com/ph-electrode-maintenance-calibration-guide

 

[Malum Argenteum]

Thanks, DDon. I think that's what caused my problem -- not rehydrating the probe before calibrating it. I wish the vendor and 'manufacturer' (re-brander, really) would've clued me in to the fact that a dry probe needs a little extra preparation.

Hopefully rehydrating in tank water is good enough, because that's what it is doing now.

 

[Malum Argenteum]

Well, this probe seems to have stabilized. It ultimately (after being calibrated without proper rehydration) ended up erratic by 1.2 units (it was reading high). I recalibrated 18 hours ago (after the probe had been sitting in the tank water for about 4 days) and it now reads dead on accurate.

The moral of the story is to rehydrate a dry pH probe for a couple days before attempting to calibrate it. Now I know. Thanks for all the replies.

 

[DDon]

Well, this probe seems to have stabilized. It ultimately (after being calibrated without proper rehydration) ended up erratic by 1.2 units (it was reading high). I recalibrated 18 hours ago (after the probe had been sitting in the tank water for about 4 days) and it now reads dead on accurate.

The moral of the story is to rehydrate a dry pH probe for a couple days before attempting to calibrate it. Now I know. Thanks for all the replies.

Glad it worked out for you.